The invention concerns a flexible pressure pipe with an associated end-fitting having an axially extending through opening, where the pipe is of a non-bonded structure comprising a number of layers including an extruded polymer inner lining extending into the through opening.
Flexible pressure pipes are used for a variety of applications, including water supply lines, sewage lines and lines for transporting chemicals such as liquid ammonia and phosphoric acid and also high pressure offshore flexible pipes for the oil and gas industry.
The joint between the inner lining and the end-fitting must be able to resist the axial tensile load acting on the inner lining, when the flexible pipe is descending over a great length, and also such stresses which arise as a consequence of temperature fluctuations.
Conventionally, said joint is provided by squeezing the inner lining between an outer conical ring and an inner conical ring which is pressed in between the inner lining and the carcass of the pipe. The effect of this squeezing will, however, diminish gradually as the plasticizer disappears from the plastic material of the lining.
Another drawback is that temperature stresses can arise in the joint because the plastic material has a high coefficient of expansion.
In the document GB 891 611 A is described a tamber-proof fitting for attachment to the end of a hose having a liner of substantially plastic material with a braided covering thereon. By assembling, an end of the liner is squeezed between an inner nipple and an outer body member having, on the innerside, sharp ribs which by the squeezing is forced into the material of the liner forming complementary share grooves in the liner. This known technique cannot be used for pipes having an inner carcass which not allows the liner to be squeezed and the nipple to be screwed in. Furthermore, the share grooves in the liner functions with a dangerous notch effect which is not acceptable for high-quality flexible pressure pipes exposed to high loads.